The present invention is in the field of retractable writing tools, and more particularly, to writing tools that employ volatile inks that evaporate when exposed to air. Still more particularly, the present invention relates to writing tools having a self sealing valve that seals the writing tip from outside air and prevents the release of vapor fluid from within the valve. The self sealing valve also allows the writing tip to be protracted through the valve, and retracted back into the valve.
Existing writing tools that use volatile fluids include a cartridge that holds the fluid supply and secures the writing tip, and a cap that protects the fluids from evaporating. In use the cap is removed from the cartridge and stored on the back end of the writing tool. Hence, existing writing tools that use volatile fluids generally require two free hands to operate and tightly sealing caps to minimize the writing tips exposure to air. Failure to replace the cap tightly from this type of dispenser causes the fluid to evaporate, and dry up the fluid after a short time. To open and store the cap requires two free hands, one to remove the cap and the second to hold the body securely. The use of two free hands to remove the cap from the body may be undesirable to the user if they only have one free hand.
Many writing tools fall into two categories: a retractable type and a non-retractable type. The distinction between these two types of writing tools usually depends on the type of fluid that is used. The fluid in the retractable type has a low evaporation rate so that even though the tip is exposed to the air, the writing tip will not dry out. In contrast, the fluid in the non-retracting type has a higher evaporation rate than the fluid in the retractable type so that the fluid can evaporate through the tip and into the air. This can cause the tip in the non-retractable type to dry out. Thus, a cap is needed to seal the tip of the non-retractable writing instrument from the air.
A ballpoint pen is a good example of a retractable writing tool that includes an internal mechanisms to allow the tip to move back and forth inside the front cowling of the pen. Retractable writing tools are convenient to use because with one hand, a user can press and release the plunger back and forth to cause the tip to move back and forth. Once the tip is in the retracted position, the tip is protected from accidentally drop and cannot accidentally write onto a surface.
A permanent marker is a good example of a non-retractable writing instrument that needs a cap to seal the tip from outside air. If the cap is left off the marker, lost or not secured properly, the tip would eventually dry out. This can shorten the life of the marker. As such, users have to remember to put the cap back on after each use. For users, however, remembering to put the cap back on after each use can be inconvenient and inefficient. Besides being inconvenient and inefficient, misplaced caps can be a choking hazard for small children.
To eliminate the need for a cap, others have designed a writing tool with a retractable tip that is sealed from the outside air when in the retracted position. The tip is sealed by incorporating some type of a sealing cover around the tip that opens to allow the tip to move in and out of the sealing cover. These sealing covers however, are complex and fail to seal the tip from outside air. In addition, the sealing covers fail to eliminate the loss of vapor fluid that is built up within the sealing covers from escaping through the openings when the writing tip is retracted back into the sealing covers. The sealing covers are also made of materials that are permeable so that vapor fluid can escape through the walls of the sealing covers as well.
In addition to the problem with the tip being exposed to air and vapor fluid escaping through the openings of the sealing cover, current retractable writing tool designs with sealing covers use permeable materials in the fabrication of the sealing covers. Accordingly, there is a need for a retractable writing tool that can seal the tip in the retracted position from outside air and the loss of vapor fluid that is built up within the sealing cover when the writing tool is in the retracted position.